Process for treating hydrocarbons



Nov. 3, 1942. H. E. DRENNAN 2,300,877

PROCESS FOR TREATING HYDROCARBONS Filed Aug. 12, 1940 BIJBWVHD.

aaawvm NOILVZIHOA'IHQQO VACUUM LINE INVENTOR H. E. DRENNAN Patented Nov. 3, 1942 2,300,877 raoenss ron 'mns'r'mo mnoosimoss Harry E. Brennan, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application August 12, 1940, Serial No. 352,299

3Claims.

An object of this invention is to provide an improvedprocess for refining hydrocarbons.

A further object of this invention is to provide an improved processior the removal of sulfur from hydrocarbons.

The applicant has discovered a new and improved process for treating hydrocarbons to improve the color and gum stability and to render them sweet to the doctor test. The process is carried out by vaporizing hydrocarbon fractions containing mercaptan sulfur and passing the vapors into contact with a desulfurization catalyst under such temperature and pressure conditions as will be hereinafter set forth. The mercaptan sulfur is removed and retained by the catalyst and the vapors may then be passed at suitable hydrogenation temperature into contact with ,a hydrogenation catalyst to hydrogenate the unstable constituents which are responsible for color and gum instability. The conditions under which the desulfurization is carried out in the applicant's process are such that the mercaptan sulfur is removed without the formation of undesirable quantities of hydrogen sulfide. This P rmits the use of desulfurizationin combination with relatively low pressure hydrogenation.

In carrying out this process for refining gasoline or other. petroleum hydrocarbons the desulfurization and hydrogenation are preferably carried out at substantially the same pressures. In actual practice the pressure at which hydrogenation is carried out may be slightly lower than the desulfurization pressure due to the resistance of flow or the gases through the desulfurizatlon catalyst. Using iron oxide as a desulfurization catalyst, the process has been operated successfully at pressures of 5 to 500 pounds per square inch gauge. A pressure of 50 pounds per square inch gauge has been found to be satisfactory. The operating pressure may be varied as the condition of the catalyst varies with use, for example a lower pressure may be used with a very active catalyst while a higher pressure may be necessary with a partly spent catalyst to effectively hydrogenate the hydrocarbon fracticn to the stability desired. with the iron oxide catalyst the desulfurlzation is preferably carried out iii the range of 500 F. to 850 F. This range includes optimum temperatures for desulfurization with ferrous oxide, ferric oxide, or both as catalysts. Mercaptan sulfur is readily removed with ferric oxide in the temperature range between 700 F. and 750 F. at superatmospheric pressures. The ferric oxide catalyst may be reduced to ferrous oxide with hydrogen or carbon monoxide in known manner. The applicant has found that ferrous oxide effects removal of mercaptans from the hydrocarbons in the temperature range around 550 F. at superatmospheric pressure. In the present process it is desirable that the operating temperature be high enough to remove all mercaptan sulfur but not so high that the sulfur compounds will be converted to hydrogen'sulfide and pass out with the hydrocarbon vapors. The hot vapors from the desulfurlzation step as carried out by the present ,invention may be passed directly into contact with the hydrogenation catalyst without necessity of further treatment for the removal of sulfur. The advantages of this process will be apparent to those skilled in the art. A hydrogenation catalyst that is susceptible to poisoning by hydrogen sulfide may be used in conjunction with the desulfurization step. If the hydrogenation catalyst is not susceptible to poisoning by hydrogen sulfide, higher desulfurization temperatures will not be detrimental to the hydrogenation catalyst by reason of hydrogen sulfide formation, but the applicant has found that higher temperatures are unnecessary with the present process. The desulfurization catalyst may be heated to the proper temperature by preheating the vapors to be refined to such a temperature that the vapors heat the catalyst to the required extent upon contact therewith or the catalyst may be heated by any other suitable means. The desulfurization step may be operated at a temperature higher than that required in the hydrogenation step, so that the hot vapors will heat the hydrogenation catalyst upon contact or the hydrogenation catalyst may be heated by any other suitable means. The hydrocarbon vapors from the iron oxide catalyst are sweet to the doctor test and free from hydrogen sulfide.

The temperature at which the sweet hydrocarbon vapors may be hydrogenated depends in part upon the catalyst used, the type of hydrocarbon fraction being hydrogenated and the degree or extent to which it is desired to hydrogenate the hydrocarbon. Factors such as pressure, temperature, rate, and hydrogen concentration, may be varied to effect the desired degree of hydrogenation. In hydrogenating a cracked gasoline from a Texas Panhandle crude oil over a reduced nickel catalyst at 50 pounds per square inch gauge pressure and at a rate of two volumes of liquid hydrocarbon (cracked gasoline) per volume of catalyst per hour, a temperature of 450 F. was found to be sufficient to improverthe color from to +30 Saybolt and increase the induction period from 4 hours to 16 hours. p

In the desulfurization step any suitable catalyst which will remove mercaptan sulfur without the formation of hydrogen sulfide may be used. Metallic oxides including copper oxide, iron oxide and nickel oxide have been found to be suitable catalysts. Regeneration of the catalyst is a factor to be considered in its selection. Ferrous sulfide, for example, reacts readily with oxygen at 700 F. The iron oxide catalyst may be regenerated in situ by flushing out the tower containing the spent catalyst with steam at 700 F. and then passing air through the catalyst to convert ferrous sulfide to iron oxide. The reaction is exothermic and requires no addition of heat, but steam may be used to control the temperature during regeneration. Other oxide catalysts may be regenerated in asimilar manner. Metals, including iron and copper, may be used as catalysts and regenerated by oxidation and reduction.

The figure is a diagrammatic elevation view of a plant suitable for carrying out the process according to the present invention. With reference to the figure, the hydrocarbons to be refined are fed as liquid to the system through the pipe i into the top of the stabilizer 2 and flow downward over suitable baiiles or bubble plates 3. Sweet gas is introduced to the bottom of the stabilizer through pipe 4. The removal of light ends and hydrogen sulfide is accomplished in the stabilizer at subatmospheric pressure by the action of the sweet gas passing in countercurrent to the hydrocarbon liquid. The light ends, gas, and hydrogen sulfide leave the top of the stabilizer through the vacuum line 5 from which they may be passed to a gasoline recovery plant not shown in the drawing. Liquid from the base of the stabilizer fiows through the float controlled valve 6 and pipe 1 to the pump 8. Pump 8 discharges the liquid hydrocarbons through valve 9 and pipe l0 into the heating coil ii of furnace I! at superatmospheric pressure, for example 50 pounds per square inch gauge. From the furnace the hydrocarbons at 500-850" F. pass through pipe i3 and valve it into the catalyst chamber is. The catalyst chamber i5 is filled with a suitable desulfurization catalyst, for example ferrous oxide which has been screened to 16 to mesh to reduce its resistance to fiuid now. The

hot hydrocarbon vapors are contacted by the catalyst which is maintained at the desired temperature by the heat from the vapors. Ferrous oxide catalyst reacts with the mercaptan sulfur in the vapors and some of the ferrous oxide is converted into ferrous sulfide. Sweetened hydrocarbon vapors are withdrawn from the catalyst chamber I 5 through the pipe i6 into a second catalyst chamber I! which contains an active hydrogenation catalyst, for example reduced nickel on a 16-30 mesh pumice base. The catalyst is maintained at the desired temperature by the hot vapors which are mixed with hydrogen as they enter the catalyst chamber H. The mixture passes over the catalyst bed where it is. partially hydrogenated. The partially hydro-- genated vapors and unreacted hydrogen flow from the catalyst chamber I! through valve i8 and pipe iii to a condenser 20 in which the hydrocarbon vapors are condensed. The condensate and hydrogen pass from condenser 211 through pipe 2| to the run tank 22 where the condensate is separated from the hydrogen and light hydrocarbon vapors. The condensate from the run tank passes through the float controlled valve 24 and pipe 25 to storage. Hydrogen and light vapors from the top of the run tank flow through pipe 26 and valve 2'! to compressor 28 from which they are discharged "through pipe 29 and valve 30 into the catalyst chamber II where it is mixed with incoming hydrocarbon vapors. Hydrogen is thus recycled at the rate of to 400 cubic feet per barrel of hydrocarbon condensate. Make-up hydrogen enters the system through pipe 3|, valve 32 and pipe 33 to the intake of the compressor 28 where it is mixed with the recycle stream ofhydrogen.

When the iron oxide or other catalyst in the catah'st chamber is becomes spent, the catalyst chamber i5 is flushed with steam entering through the pipes II, 14, and the valve 35 to remove most of the hydrocarbon vapors. The air may then be introduced through the same pipes 3i, 34 to regenerate the catalyst. The iron oxide catalyst is preheated by the steam to a temperature at which air will react with the iron sulfide to raise the temperature to about 120071. The temperature may then be controlled during the regeneration by admission of steam with the air. The iron sulfide is oxidized to iron oxide and the sulfur burnsto sulfur dioxide and passes out of the catalyst chamber through valve 36 with the air and steam. After the oxidation of the ferrous sulfide to iron oxide (prin p ric oxide), the iron oxide may be reduced with hydrogen or carbon monoxide or a mixture at a temperature between 750 F. and 1,000 P. until the ferric oxide is substantially all reduced to ferrous oxide. The catalyst is then readyfor further use to desulfurize the hydrocarbon vapors. steam, air, and hydrogen may be admitted to the catalyst chamber il through the valve 36 for regeneration of the hydrogenation catalyst.

The iron oxide catalyst has been used until 45% of the oxide was converted to the sulfide. This is equivalent to operation for 45 days with a charging rate of two volumes of liquid hydro-- carbon per volume of catalyst per hour. The life of the nickel catalyst has not been determined but it has been run 45 days at the above charging rate. The long life of the nickel catalyst is due in part to the fact that at the temperature of operhtion for hydrogenation no desulfurization takes place- If the nickel catalyst becomes inactive or spent it may be regenerated in the same manner as that described for the iron oxide, by oxidation with air followed by reduction with hydrogen. It is necessary to heat the air to maintain a temperature sumciently high in the nickel catalyst chamber to oxidize the nickel sulfide to the oxide. Reduction can be carried out at 750' F. to 850' F.

Example I Raw cracked gasoline made by cracking gas oil from a Texas Panhandle crude oil of high sulfur content was vaporized and contacted with ferrous oxide at 550 F. and 50 pounds per square inch gauge pressure at the rate of two volumes of liquid gasoline per volume of catalyst per hour for removal of mercaptan sulfur. The hot vapors from the ferrous oxide were mixed with four cubic feet of hydrogen per gallon of gasoline and contacted with an equal volume of catalyst comprising nickel on a refractory material at pounds per square inch gauge.

Mixing of cool hydrogen with the 550 F. vapors was sufiicient to maintain the temperature of the hydrogenation catalyst at approximately 450 F. Tests made on the gasoline before and after refining were as follows:

Charge Make Gravity, A. P. I 55. 6 55. Color +17 +30 Percentage sulfur"... 155 lO-i Induction period (hrs. 4 16 Percentage unsaturatesv 14 12 Percentage aromatics-.- 28 24 Reid vapor pressure... 6.1 r 4. 3 Initial boiling point.. 110 115 Percentage at 212 F-- 22 21 End point 408 410 Octane number (L-3) 60. 8 61.0 Octane number-H cc. TEL 1 (L3) 67.0 68. 6 Octane number+2 cc. TEL 1 (11-3). 71.2 73.0 Octane number-k3 cc. TEL I (Ii-3) 73. 5 73.3

K Tetraethyl lead.

The sample in the above example was weathered, which is responsible for the low values for the gravity, percentage distilled at 212 F., Reid vapor pressure, and octane number.

It will be noted that the pressure and temperature conditions of the present process are such that the treatment may take place in liquid phase.

I claim:

1. A process of treating a hydrocarbon fraction containing mercaptan sulfur and colorand gum-forming constituents to render it sweet to the doctor test and improve its colorand gumstability which comprises desulfurizingsaid fraction by contact at a pressure of 5 to 500 pounds per square inch gauge and at a temperature of 500 to 850 F. with a metal oxide capable of reacting with mercaptan sulfur to form the corresponding sulfide under conditions and for a contact time such that substantially all of said mercaptan sulfur is removed and retained by said metal oxide and that no hydrogen sulfide is formed and no hydrogen sulfide is contained in the eiiiuent, commingling the hot eflluent with hydrogen, and passing the resulting mixture at a hydrogenating temperature below said desuliurization' temperature and such that no desuliurlzation takes place and at a pressure substantially equal to said desulturization pressure over a hydrogensulflde-poisonable hydrogenation catalyst to hydrogenate the unstable constituents which are responsible for colorand gum-instability, said process being carried out without decrease in the octane number and lead-susceptibility of said traction.

2. A rocessor treating raw cracked gasoline containing mercaptan sulfur and colorand gumforming constituents to render it sweet to the doctor test and improve its colorand gum-stability and give it a color of at least 30, which comprises desuli'urizing said gasoline by contact at a pressure oi. 5 to 500 pounds per square inch gauge and at a temperature 01 500 to 850 F. with ferrous oxide under conditions and for a contact time such that substantially all 0! said mercaptan sulfur is retained by said ferrous oxide and that no hydrogen sulfide is formed and no hydrogen sulfide is contained in the efiluent, comminglingthe hot eilluent with hydrogen, and passing the' resulting mixture at a hydrogenating tempera ture lower than said desuliurization temperature and such that no desulturization takes place and at a pressure substantially equal to saiddes'uliurization pressure over a hydrogen sulfidepoisonable reduced nickel hydrogenation catalyst to hydrogenate the unstable constituents which are responsible for -color-and gum-instability, said process being carried out without decrease in the octane number and lead susceptibility of said cracked gasoline.

3. A process as recited in claim 2 wherein said desulrurization step is conducted at. about pounds per square inch gauge and at a temperature of about 550 F. and wherein said hydrogenation is conducted at about the same'pressure but at a temperature of about 450 F.

HARRY E. DRENNAN.

GERTIFIGATE on'o'o'mmqn. I Patentlo. ,3 ,877 I V a Y I I p mm 1:. annual; It is hereby certifie d'that e'rr'qi'abpears 1n the printed pedifta'tio n of the above numbered patent requ i rln'g correction as follows; Pa g 5; first column, in the mu last .line' thereof, for 975.5" ro'ad --7 .5--; and that the said Letters Patent should be ead with this correctidn therein that the same may -con foi'm to the record of the cas in th Patenfi Office. l

Signed and sealed this 29th day of December, 1334.2.

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